Hitherto, a belt conveying device that conveys a recording medium such as a sheet by using a belt stretched around a plurality of rollers has been practically used. In such a belt conveying device, there is known a problem in which, during circulation movement of the belt, the belt skews in a widthwise direction of the belt due to an external force applied from a photosensitive member, a change in temperature, and a variation in component accuracy.
To regulate the above-described skewness, in a belt-type fixing device that transmits heat to a recording medium by a fixing belt stretched around a fixing roller and a heating roller, a guide ring that regulates the skewness of the fixing belt is provided at at least one axial end of the rollers. The tensile force of the fixing belt is adjusted by moving the heating roller so that the distance between the heating roller and the fixing roller is shortened in response to an increase in the temperature of the heating roller, and the guide ring is separated from the fixing belt so as to prevent the damage in the fixing belt.